1. Field of the Invention
The present invention relates generally to disk cartridges and more particularly to a disk cartridge which can prevent the disk surface from being damaged or the like when a disk is exchanged and which includes a write-protecting mechanism to determine whether or not an information signal is recorded on a disk.
2. Description of the Prior Art
There has conventionally been proposed a disk-shaped record medium, such as, a so-called write once optical disk in which an information signal can be recorded and a rewritable optical disk from which the recorded information signal can be erased. This disk-shaped record medium is generally accommodated in some suitable disk cartridge in order to prevent it from being smudged by dust or the like when it is not loaded onto a recording and/or reproducing apparatus, i.e., upon non-use. Also, the disk-shaped record medium is accommodated in the disk cartridge in order to protect it from being damaged when it is brought in contact with other discs. It should be noted that when the disk-shaped record medium is damaged as described above, an error occurs in the writing and/or reading operation of the information signal. For simplicity, the disk-shaped record medium will, hereinafter, be referred to as a disk.
For example, U.S. Pat. Nos. 4,669,078 and 4,460,930 disclose this kind of disk cartridge. This disk cartridge is provided with an opening portion through which a part of the disk is exposed in a range of its outer periphery to its central portion along the diametrical direction thereof by a predetermined width. When the disk cartridge is loaded on the recording and/or reproducing apparatus while accommodating the disk therein, the disk can be recorded on and/or reproduced from by the pickup device of the recording and/or reproducing apparatus through the opening portion. This opening portion is formed such that when the disk cartridge is loaded on the recording and/or reproducing apparatus, a disk turn table is provided within the recording and/or reproducing apparatus-body to rotate the disk. A chucking member which rotates the disk in cooperation with the disk turn table, is opposed to the central portion of the disk through this opening portion. The pickup device of the recording and/or reproducing apparatus is opposed to the signal recorded portion of the disk. Further, the disk cartridge is provided with a sliding shutter which is slidably fitted to one side wall of the disk cartridge, for example, to the front surface thereof in the direction in which the disk cartridge is inserted in to the recording and/or reproducing apparatus. This sliding shutter is adapted to open and close the opening portion of the disk cartridge. The sliding shutter is restricted in its slidable movement when it is located at a position in which the opening portion of the disk cartridge is closed thereby, namely, the closing position. The thus arranged sliding shutter can be prevented from being opened inadvertently so that the disk is protected from dust and so on entering therein via the above opening portion.
Furthermore, U.S. Pat. No. 4,460,930 discloses the disk cartridge that is provided with a write-protecting mechanism. According to this write-protecting mechanism, it is possible to prevent the previously-recorded information on the disk from being damaged when a different information signal is recorded or erased by a head assembly of the recording and/or reoproducing apparatus from the portion in which the information signal is already recorded. The above
U.S. Pat. No. 4,460,930 discloses the write-protecting mechanism fitted to the disk cartridge at its corner portion of the rear wall side, or at its end edge opposing to the side in which the sliding shutter is provided. The write-protecting mechanism disclosed in U.S. Pat. No. 4,460,930 is adapted to determine by the position of the detecting element, slidable within the detecting opening portion formed through the disk cartridge-body, whether or not the recording of the information signal on the disk is permitted. When the thus arranged disk cartridge is loaded in the recording and/or reproducing apparatus, the detecting element can be detected by detecting means such as a switch or the like provided in the recording and/or reproducing apparatus-body. Simultaneously, the detecting element of the disk cartridge can be visually confirmed by the user.
When the disk cannot be recorded and/or reproduced due to some factors or the disk cartridge is broken while the disk is normal, either the disk cartridge or the disk becomes useless. To remove the above defects, there is proposed such a disk cartridge as disclosed in U.S. Pat. No. 4,669,078. According to the disk cartridge disclosed in U.S. Pat. No. 4,669,078, the disk accommodated therein can be exchanged. That is, this disk cartridge is formed of a pair of upper and lower cartridge halves. According to this disk cartridge, the upper cartridge half is fitted to the lower cartridge half provided with a disk accommodating portion so as to become openable and closable, thus permitting the exchange of the disk.
The disk cartridge disclosed in U.S. Pat. No. 4,460,930 may be modified into the disk cartridge disclosed in U.S. Pat. No. 4,669,078 in which the disk accommodated therein can be exchanged. In that case, an opening portion that allows the disk to be exchanged has to be formed on the rear wall side of the disk cartridge and an openable and closable member to open and close the above-mentioned opening portion has to be formed. The reason therefor is as follows. If the opening portion and the openable and closable member are provided on the disk cartridge-body at its one side wall of both side walls in parallel to the direction in which the disk cartridge is loaded on the recording and/or reproducing apparatus, when the disk cartridge is loaded on or ejected from the recording and/or reproducing apparatus, the openable and closable member is raised up from the disk cartridge-body to be caught by a loading mechanism of the recording and/or reproducing apparatus. There is then a risk that the disk cartridge will not be loaded on or ejected from the recording and/or reproducing apparatus. Eventually, the disk cartridge cannot be stably loaded on or ejected from the recording and/or reproducing apparatus. This leads to trouble in the recording and/or reproducing apparatus.
If the opening portion and the openable and closable member are provided at the rear wall side of the disk cartridge-body, the following problems arise.
Specifically, the write-protecting mechanism is provided at the rear wall side of the disk cartridge-body so that when the opening portion is formed on the same rear wall side, the write-protecting mechanism hinders the exchange of the disk. Further, the write-protecting mechanism protrudes from the inner surfaces of the pair of upper and lower cartridge halves forming the disk cartridge-body of the disk cartridge so that when the disk is exchanged, the disk surface comes in contact with the write-protecting mechanism, whereby the disk surface is scratched or damaged. If the thus damaged disk is recorded on and/or reproduced from by the recording and/or reproducing apparatus, an error occurs in the writing and/or reading operation of the information signal. The result is that the normal recording and/or reproduction is impossible.